First Steps (Phosh)
This page is about running postmarketOS for the first time, after it was installed with the Phosh user interface. Note that the first boot takes longer than usual, as the file system will be resized to use the entire device. The first start of Firefox also takes longer than the following starts.
Install updates and reboot

Unless you have just built your own postmarketOS image a few minutes before doing the installation, it is highly recommended to install updates and then reboot your device. To do that, open the "Software" app, tap the "Updates" button on the bottom right. Then tap "Update All".
Once all updates are installed, reboot so you are actually using the newly installed software and not still the old versions. To do that, tap the top bar between the clock and the battery icon, then tap the power symbol.
Do not report issues unless you have made sure that you have rebooted into an up-to-date system.
SSL handshake failed notification
The notification 'Unable to download updates from "odrs.gnome.org" ... SSL handshake failed' can be ignored. Just tap the "x" at the bottom, so it does not cover the "Update All" button anymore.
This message appears if you have just connected to Wi-Fi, and your device's date was not synced with the Internet yet (see the clock that is visible in the top bar). Then GNOME software will fail to download some software ratings via the secure HTTPS protocol, because it can't verify the server's certificates without knowing the date (as they could have expired). For our use case, this is all irrelevant: we don't need the software ratings right now, we want to do updates. Because these updates are signed with a different mechanism already, we don't use HTTPS, but instead the plain HTTP to download them. So we don't even need to have the date synced.